Fighter aircraft are normally equipped with ejection seats that allow the pilot and any additional crew to safely escape the aircraft in the event the aircraft is disabled either through mechanical malfunction or hostile action. These ejection seats are typically propelled from the aircraft at very high velocities by rocket boosters so that the seat and pilot can eject quickly and then clear the tail of the aircraft. The high velocity required for successful ejection requires that the seat and pilot undergo a great deal of acceleration. Also, once the seat and pilot have been ejected, the airflow around the pilot subjects the pilot to rapid deceleration and aerodynamic buffeting. These accelerations, decelerations and aerodynamic buffeting can severely injure the pilot unless the pilot is properly positioned and securely restrained in the seat during ejection.
The pilot obviously could be restrained in the ejection seat by fixed straps securing the pilot to the ejection seat. However, it is necessary for the pilot to be able to move freely in the ejection seat at various times while flying the aircraft. For example, the pilot must check the six o'clock position often during some fight maneuvers to be sure that hostile aircraft are not on the aircraft's tail. In order to check the six o'clock position, the pilot must rotate his or her torso away from the back of the seat. However, it is not possible to perform this maneuver if the pilot is tightly restrained in the seat. It is therefore necessary to allow the pilot to move freely in the ejection seat during flight but be quickly positioned and restrained prior to and during ejection.
One prior art system for positioning and restraining a pilot in a seat prior to ejection yet allowing freedom of movement at other times is a powered reel system. Powered reel systems utilize restraining straps that either surround the pilot's torso or are connected to a harness surrounding the pilot. The restraining straps extend to and are wound on respective spring-loaded reels that maintain a relatively slight tension on the straps but otherwise allow the straps to be freely extended from the reels. The reels may or may not have an inertia locking system that locks the reels in the event that the respective straps unwind from the reel at an excessive rate. In either case, the reels are connected to a rotational drive mechanism that is energized just prior to ejection to rotate the reels and retract the restraining straps to pull the pilot back into the ejection seat. These "haulback" systems, as they are commonly called, typically utilize a gas-powered motor as the rotational drive mechanism and a pyrotechnic gas generator to supply pressurized gas to the motor.
Conventional gas-powered haulback systems suffer from two primary limitations. First, they are sometimes incapable of generating sufficient force and/or retracting the straps with sufficient speed to adequately position and restrain the pilot prior to ejection. As a result, the pilot can be severely injured or even killed. Second, the conventional gas-powered haulback systems sometimes generate excessive haulback forces. These excessive haulback forces can cause the pilot's torso to be accelerated to excessive velocities so that the pilot strikes the back of the ejection seat with excessive force, thereby injuring the pilot. As a result, these excessive haulback forces can also seriously injure the pilot.